Counterfeit Combat: Hardest Notes to Fake

More From American Greed

Anti-Counterfeiting Around the World

In the United States alone, there's an estimated $70 million in fake currency floating around. Fortunately, as the technology counterfeiters use improves, so does that of authentic bills.

All across the globe, experts are devising high-tech methods to combat counterfeiters. Color-changing ink, special polymers and holographs are just some of the innovative technologies incorporated into today's banknotes.

In 2007, the International Association of Currency Affairs began picking the best new counterfeiting technologies and tactics. They'll award this year's winners at the 2010 Currency Conferece in Buenos Aires in early May.

Click ahead to see some of the world's currencies that are most impervious to fraud.